Sump safety / pressure relief valve

ASME-rated relief on the separator tank set at or below the vessel MAWP — the last line of defence.

Also called: PRV · pop-off valve · ASME relief

Normally closed. Never plug, gag, or adjust — replace instead.

How it works

A spring-loaded pop valve set above normal operating pressure but at or below the sump's stamped MAWP. It lifts fully at set pressure and reseats after the overpressure clears.

Specifications

Typical settings

Set at or below the tank data plate MAWP; commonly 150, 175 or 200 PSIG

Standard

ASME Section VIII / UV stamped for air receivers and sumps

Service

Replace on any lift, leak, or per the OEM interval (commonly annually)

Parts you can order

• Generic ASME (Kunkle / Conbraco class)

  ASME section VIII air relief valve

  Select by set pressure and SCFM capacity

  $45 – $300
• Kunkle (Emerson)

  Series 337 ASME air relief valve

  337 (specify size and set pressure)

  $70 – $380
• Apollo / Conbraco

  ASME air safety relief valve

  By size and set pressure

  $45 – $240
• Control Devices

  SR series ASME safety valve

  SR25A-175 (example: 1/4 in., 175 psi)

  $15 – $70

Field test procedure

1. Do not lift-test a valve on a hot pressurised sump as routine maintenance — modern practice is replacement on schedule.
2. A valve that has lifted once and reseated leaking is scrap.
3. If it lifts in service, find the real cause: unload failure, blocked MPV, or a closed service isolation valve.

Symptoms & probable causes

• Relief lifting during normal running
  Machine won't unload — load solenoid, inlet valve, or controller setpoint.
• Weeping relief
  Debris on the seat or a previously lifted valve. Replace.